[clang] [libc++] Prevent calling the projection more than three times (PR #66315)

[via cfe-commits]

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@@ -37,9 +37,10 @@ struct __fn {
     _LIBCPP_ASSERT_UNCATEGORIZED(!bool(std::invoke(__comp, std::invoke(__proj, __high), std::invoke(__proj, __low))),
                                  "Bad bounds passed to std::ranges::clamp");
 
-    if (std::invoke(__comp, std::invoke(__proj, __value), std::invoke(__proj, __low)))
+    auto&& __projected = std::invoke(__proj, __value);
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timsong-cpp wrote:

The `invoke(__proj, __value)` call itself creates no temporaries; it just binds two references. Any temporaries are created inside `invoke` and are destroyed before `invoke` returns, so `invoke(identity_proj, "")` is always dangling regardless of what you do with the result.

https://github.com/llvm/llvm-project/pull/66315